The Zodiacal Light

Over the eons, as comets shed dust and asteroids collide, dust particles are freed from their parent bodies and, for a time, orbit independently around the Sun. These tiny particles (typically 1 to 300 μm across) reflect sunlight that can be seen from Earth. This phenomenon is called the zodiacal light (pronounced zoe-DYE-uh-cul). It is a subtle yet beautiful cone of white light most easily seen extending up from the western horizon at the end of evening twilight, or projecting above the eastern horizon just before morning twilight begins. This phenomenon is named after the zodiac because the dust is concentrated near the plane of the ecliptic. The picture is complicated by the fact that there are zodiacal dust components that lie along the solar equatorial plane, the orbital plane of Venus, the invariable plane of the solar system, and the ecliptic. All four of these reference planes lie within a few degrees inclination of each other.

Since the zodiacal light is generally brightest along the ecliptic just a few degrees away from the Sun, it is best to pick a time of year when that portion of the ecliptic is most nearly perpendicular to the horizon to make your observations. This, of course, depends on your latitude (closer to the equator being better), but for those of us here in the Midwest, February, March, and April offer the very best times to see and photograph the zodiacal light above the western horizon at the end of evening twilight. The very best times to see and photograph the zodiacal light above the eastern horizon before the beginning of morning twilight occurs for us in August, September and October.

In the images below, the yellow line is the ecliptic. A mid-month view for each month of the year, morning and evening, is shown for latitude 43° N. Note that the best months for viewing evening and morning zodiacal light listed above show the ecliptic at the steepest angles relative to the horizon.

In this year of 2017, the best dates and times for observing the zodiacal light are listed below. The sky must be very clear. The specific times listed are for Dodgeville, Wisconsin.

2017

Begin

End

Direction

Sun. Feb. 12

7:03 p.m.

7:32 p.m.

West

Mon. Feb. 13

7:05 p.m.

8:05 p.m.

West

Tue. Feb. 14

7:06 p.m.

8:06 p.m.

West

Wed. Feb. 15

7:07 p.m.

8:07 p.m.

West

Thu. Feb. 16

7:08 p.m.

8:08 p.m.

West

Fri. Feb. 17

7:09 p.m.

8:09 p.m.

West

Sat. Feb. 18

7:11 p.m.

8:11 p.m.

West

Sun. Feb. 19

7:12 p.m.

8:12 p.m.

West

Mon. Feb. 20

7:13 p.m.

8:13 p.m.

West

Tue. Feb. 21

7:14 p.m.

8:14 p.m.

West

Wed. Feb. 22

7:15 p.m.

8:15 p.m.

West

Thu. Feb. 23

7:17 p.m.

8:17 p.m.

West

Fri. Feb. 24

7:18 p.m.

8:18 p.m.

West

Sat. Feb. 25

7:19 p.m.

8:19 p.m.

West

Sun. Feb. 26

7:20 p.m.

8:20 p.m.

West

Mon. Feb. 27

7:22 p.m.

8:22 p.m.

West

Tue. Mar. 14

8:40 p.m.

9:22 p.m.

West

Wed. Mar. 15

8:42 p.m.

9:42 p.m.

West

Thu. Mar. 16

8:43 p.m.

9:43 p.m.

West

Fri. Mar. 17

8:44 p.m.

9:44 p.m.

West

Sat. Mar. 18

8:46 p.m.

9:46 p.m.

West

Sun. Mar. 19

8:47 p.m.

9:47 p.m.

West

Mon. Mar. 20

8:48 p.m.

9:48 p.m.

West

Tue. Mar. 21

8:50 p.m.

9:50 p.m.

West

Wed. Mar. 22

8:51 p.m.

9:51 p.m.

West

Thu. Mar. 23

8:52 p.m.

9:52 p.m.

West

Fri. Mar. 24

8:54 p.m.

9:54 p.m.

West

Sat. Mar. 25

8:55 p.m.

9:55 p.m.

West

Sun. Mar. 26

8:56 p.m.

9:56 p.m.

West

Mon. Mar. 27

8:58 p.m.

9:58 p.m.

West

Tue. Mar. 28

8:59 p.m.

9:59 p.m.

West

Wed. Mar. 29

9:27 p.m.

10:01 p.m.

West

Thu. Apr. 13

9:23 p.m.

10:07 p.m.

West

Fri. Apr. 14

9:25 p.m.

10:25 p.m.

West

Sat. Apr. 15

9:26 p.m.

10:26 p.m.

West

Sun. Apr. 16

9:28 p.m.

10:28 p.m.

West

Mon. Apr. 17

9:29 p.m.

10:29 p.m.

West

Tue. Apr. 18

9:31 p.m.

10:31 p.m.

West

Wed. Apr. 19

9:33 p.m.

10:33 p.m.

West

Thu. Apr. 20

9:34 p.m.

10:34 p.m.

West

Fri. Apr. 21

9:36 p.m.

10:36 p.m.

West

Sat. Apr. 22

9:38 p.m.

10:38 p.m.

West

Sun. Apr. 23

9:39 p.m.

10:39 p.m.

West

Mon. Apr. 24

9:41 p.m.

10:41 p.m.

West

Tue. Apr. 25

9:43 p.m.

10:43 p.m.

West

Wed. Apr. 26

9:44 p.m.

10:44 p.m.

West

Thu. Apr. 27

9:46 p.m.

10:46 p.m.

West

Sat. Aug. 19

3:24 a.m.

3:40 a.m.

East

Sun. Aug. 20

3:26 a.m.

4:26 a.m.

East

Mon. Aug. 21

3:27 a.m.

4:27 a.m.

East

Tue. Aug. 22

3:29 a.m.

4:29 a.m.

East

Wed. Aug. 23

3:30 a.m.

4:30 a.m.

East

Thu. Aug. 24

3:32 a.m.

4:32 a.m.

East

Fri. Aug. 25

3:33 a.m.

4:33 a.m.

East

Sat. Aug. 26

3:35 a.m.

4:35 a.m.

East

Sun. Aug. 27

3:26 a.m.

4:36 a.m.

East

Mon. Aug. 28

3:38 a.m.

4:38 a.m.

East

Tue. Aug. 29

3:39 a.m.

4:39 a.m.

East

Wed. Aug. 30

3:41 a.m.

4:41 a.m.

East

Thu. Aug. 31

3:42 a.m.

4:42 a.m.

East

Fri. Sep. 1

3:44 a.m.

4:44 a.m.

East

Sat. Sep. 2

3:45 a.m.

4:45 a.m.

East

Sun. Sep. 3

3:47 a.m.

4:47 a.m.

East

Mon. Sep. 4

4:36 a.m.

4:48 a.m.

East

Mon. Sep. 18

4:07 a.m.

4:49 a.m.

East

Tue. Sep. 19

4:08 a.m.

5:08 a.m.

East

Wed. Sep. 20

4:10 a.m.

5:10 a.m.

East

Thu. Sep. 21

4:11 a.m.

5:11 a.m.

East

Fri. Sep. 22

4:12 a.m.

5:12 a.m.

East

Sat. Sep. 23

4:13 a.m.

5:13 a.m.

East

Sun. Sep. 24

4:15 a.m.

5:15 a.m.

East

Mon. Sep. 25

4:16 a.m.

5:16 a.m.

East

Tue. Sep. 26

4:17 a.m.

5:17 a.m.

East

Wed. Sep. 27

4:18 a.m.

5:18 a.m.

East

Thu. Sep. 28

4:20 a.m.

5:20 a.m.

East

Fri. Sep. 29

4:21 a.m.

5:21 a.m.

East

Sat. Sep. 30

4:22 a.m.

5:22 a.m.

East

Sun. Oct. 1

4:23 a.m.

5:23 a.m.

East

Mon. Oct. 2

4:24 a.m.

5:24 a.m.

East

Tue. Oct. 3

4:26 a.m.

5:26 a.m.

East

Wed. Oct. 18

4:43 a.m.

5:43 a.m.

East

Thu. Oct. 19

4:44 a.m.

5:44 a.m.

East

Fri. Oct. 20

4:45 a.m.

5:45 a.m.

East

Sat. Oct. 21

4:46 a.m.

5:46 a.m.

East

Sun. Oct. 22

4:48 a.m.

5:48 a.m.

East

Mon. Oct. 23

4:49 a.m.

5:49 a.m.

East

Tue. Oct. 24

4:50 a.m.

5:50 a.m.

East

Wed. Oct. 25

4:51 a.m.

5:51 a.m.

East

Thu. Oct. 26

4:52 a.m.

5:52 a.m.

East

Fri. Oct. 27

4:53 a.m.

5:53 a.m.

East

Sat. Oct. 28

4:54 a.m.

5:54 a.m.

East

Sun. Oct. 29

4:55 a.m.

5:55 a.m.

East

Mon. Oct. 30

4:57 a.m.

5:57 a.m.

East

Tue. Oct. 31

4:58 a.m.

5:58 a.m.

East

Wed. Nov. 1

4:59 a.m.

5:59 a.m.

East

Thu. Nov. 2

5:27 a.m.

6:00 a.m.

East

On the February, March, and April evenings listed above, you will see a broad, faint band of light extending upwards from the western horizon, sloping a little to the left, and reaching nearly halfway to the top of the sky.

On the August, September, and October mornings listed above, you will see a broad, faint band of light extending upwards from the eastern horizon, sloping a little to the right, and reaching nearly halfway to the top of the sky.

It is essential that your view is not spoiled by nearby lights or any city to the west (Feb-Apr) or east (Aug-Oct). Give your eyes a few minutes to adjust to the darkness. Slowly sweeping your eyes back and forth from southwest to northwest (Feb-Apr) or northeast to southeast (Aug-Oct) will help you spot the zodiacal light band. Once spotted, you should be able to see it without moving your head.

On the February, March, and April evenings listed above, the zodiacal light is best seen right at the end of evening twilight, and remains visible for an hour or so after that.

On the August, September, and October mornings listed above, the zodiacal light is best seen about an hour or so before the beginning of morning twilight, right up to the beginning of morning twilight.